1998 Ford Contour Acceleration Problem

JDUTTO1986

1998 ALL OTHER MAKES ALL OTHER MODELS

I have a 1998 Ford Contour with about 84,000 miles. Automatic transmission/2-wheel drive. About a year ago I had to take it in to have the timing belt replaced. Just recently while accelerating from 20-40 my car feels like it's having trouble switching gears until I break 40, then things smooth over. This is slightly different from when I had the timing belt repaired as it doesn't have too much trouble hitting 40. I'd just like some advice if it would help me prevent the problem from getting worse.